1. Field of the invention
The invention relates to the field of reliability engineering. It is based on a method for determining reliability characteristics for a technical installation on the basis of the preamble to the first claim.
2. Discussion of background
A generic method has already been described in Lecture Notes in Computer Science 1150, Dependable Computing--EDCC--2, "Reliability Evaluation of a Computing System for Traction Control of Electrical Locomotives", pages 129-140, Springer Verlag, October 1996, by Silke Draber and Bernhard Eschermann.
An FMEA table is initially produced for the technical installation. FMEA tables are understood to be a list of the failure modes, failure probabilities and failure effects of all the relevant components of an installation (FMEA=Failure Modes and Effects Analysis). Using this information, it is possible to calculate the reliability characteristics (e.g. MTTF "Mean Time to Failure"). Details on how an FMEA table is produced can be found in the book "Qualitat und Zuverlassigkeit technischer Systeme" [Quality and reliability of technical systems] by A. Birolini, Springer-Verlag 1988, 2nd edition, pages 63-66. In order to calculate the reliability characteristics, the FMEA tables produced are converted into a Markov model in a subsequent step, and this can be used to calculate the characteristics.
Reliability characteristics for a technical installation are very important for the design of the installation. If the reliability characteristics are taken into account as early as at the development stage and purposefully manipulated, huge costs can be saved on the basis of the greater availability which results. Thus, for example, the analysis of reliability characteristics makes it possible to design identified weaknesses in the installation to be redundant, or to reinforce them. For this reason, it is judicious to produce FMEA tables throughout development and to calculate reliability characteristics, so that the reliability of various installation configurations can be compared. On the basis of the prior art, an FMEA table would have to be produced and reliability characteristics determined by calculation for each installation configuration separately, since failure modes, rates, probabilities and the effects of failure depend on the configuration of the installation. In a very simple installation, this can still be done using only a handful of installation configurations. In industrial practice, however, the number of configurations for the installation that have to be compared with one another using reliability characteristics is often multitudinous. Hundreds, if not thousands, of installation configurations result which it is virtually impossible to represent without computer assistance, without mentioning the fact that a specific FMEA table can be produced for each of these configurations.
The amount of work involved is so great that it is virtually impossible to avoid errors. In addition, a small modification at one point involves numerous adjustments at other points, so that calculation of the reliability characteristics becomes very inflexible. Particularly for automatic calculation of the reliability characteristics for all installation configurations of a technical installation, it would therefore be desirable if the amount of effort required could be reduced.